When it comes to sperm meeting eggs in sexual reproduction, conventional wisdom holds that the fastest swimming sperm are most likely to succeed in their quest to fertilize eggs.
However, sperm speed "is a very important parameter, and the proportion of motile sperm is positively associated and a predictor of the chance of achieving a pregnancy."
One explanation has to do with the chromosomes in sperm. The Y chromosome, which makes boys, contains less DNA than the X chromosome for girls. That means sperm that bear a Y chromosome swim faster in viscous liquids.
Now, a new study shows that even though the fastest and most capable sperms reach the ovum first, it is the egg that has the final say on which sperm fertilizes it.
In a review of 333 cases evaluated for infertility, the average sperm velocity in a normal semen analysis was 96.5 mu/sec, for those with normal postcoital test (PCT) 96.6 mu/sec, and in those that established a pregnancy 91.6 mu/sec.
There is no specific frequency with which a man should ejaculate. There is no solid evidence that failure to ejaculate causes health problems. However, ejaculating frequently can reduce the man's risk of getting prostate cancer. Ejacu-lation can be through having sex or masturbating a few times a day.
Summary: Sperm in the first fraction of ejaculate are more numerous, move more and present better quality DNA than those lagging behind.
“Human eggs release chemicals called chemoattractants that attract sperm to unfertilised eggs.
Have sex often, at least 3 times a week, the more often you try, the more chances you get at becoming pregnant. Lying down for at least a few minutes after sex increases the odds that the sperm will be able to keep their date with the awaiting egg. Make sure that you have been properly screened for STDs.
The preliminary findings indicated that X spermatozoa are larger and stronger than Y spermatozoa, suggesting that they are more stable in an acidic pH than Y spermatozoa (Landrum and Shettles, 1960; Shettles, 1960).
Shettles. The basis for the Shettles method starts with the fact that X-chromosome sperm (female) are on average slightly larger and thus slower moving than Y-chromosome sperm (male). And X-chromosome sperm live longer.
Smoking and drinking – excessive alcohol intake and use of tobacco products contribute to many health problems, so it should come as no surprise that they can both affect your sperm motility rate.
How does sperm motility affect fertility? Sperm motility is the ability of sperm to move efficiently. This is important in fertility because sperm need to move through the woman's reproductive tract to reach and fertilize her egg. Poor sperm motility can be a cause of male factor infertility.
Millions of sperm enter the race to fertilize, but only one wins the sprint to the egg. Now Yale researchers have discovered that these winning sperm possess a few key molecular characteristics that differentiate them from those left behind, they report Dec.
The concentration of sperm is what makes the semen cloudy and thick, so if your ejaculate is watery it is possible that you have a low sperm count. This doesn't mean you're infertile (so precautions to prevent pregnancy still need to be taken for couples that don't want to get pregnant).
Researchers from Stockholm University and the Manchester University NHS Foundation Trust found that the egg effectively chooses the sperm it wants, and rejects the others. "Human eggs release chemicals called chemoattractants that attract sperm to unfertilised eggs.
Occasionally, two sperm are known to fertilize a single egg; this 'double fertilization' is thought to happen in about 1% of human conceptions. An embryo created this way doesn't usually survive, but a few cases are known to have made it — these children are chimaeras of cells with X and Y chromosomes.
The cortical reaction is a process initiated during fertilization that prevents polyspermy, the fusion of multiple sperm with one egg.
Peak and Decline
Researchers found that semen quantity peaked between the ages of 30 and 35. (Could this be nature's way of making sure a couple conceives before female fertility starts to decline at age 35?) On the other end of the spectrum, overall semen quantity was found to be lowest after age 55.
That depends on many factors and can vary from time to time. Measured on a stopwatch, it takes an average of 5 to 7 minutes for a man to reach orgasm and ejaculate. But the overall range is wide, from less than one minute to over half an hour.
There are two types of sperm cells: X sperm and Y sperm. X sperm: X sperm on combining with the X chromosome of the female produces a zygote with XX chromosomes.
Use of cocaine or marijuana may temporarily reduce the number and quality of your sperm as well. Alcohol use. Drinking alcohol can lower testosterone levels, cause erectile dysfunction and decrease sperm production. Liver disease caused by excessive drinking also may lead to fertility problems.
No, you can't run out of sperm. Your testes are always making new sperm, which means you'll have a constant supply even if you're masturbating a lot and/or having sex every single day. Having said that, it is possible to have a “dry orgasm”. This is where you reach a sexual climax, but don't ejaculate any semen.